mini2440 驱动ds18b20(三)
D_MAJOR 0 //定义主设备号
#define D_MINOR 0 //定义从设备号
#define DEV_NAME "ds18b20" //定义设备名
static int ds18b20_major = D_MAJOR;//ds18b20主设备号
static int ds18b20_minor = D_MINOR;//ds18b20从设备号
static struct class *my_class; //定义class，用于自动挂载设备
static struct class_device *my_device; //自动挂载设备
static struct ds18b20_dev{ //放在一个结构体中
struct cdev cdev; //这个结构体比较简单，但是建议以后将用户的东西都放在一个结构体中
};
struct ds18b20_dev *ds18b20_devp;
void ds18b20_reset(void) //重启ds18b20
{
s3c2410_gpio_cfgpin(DQ, DQ_OUT); //设置为输出
s3c2410_gpio_pullup(DQ, 0); //设置下拉
s3c2410_gpio_setpin(DQ, 0); //拉低总线
udelay(500); //需要将总线拉低480~950us
s3c2410_gpio_setpin(DQ, 1); //释放总线
udelay(60); //DS18B20拉低信号，60~240us表示应答
s3c2410_gpio_cfgpin(DQ, DQ_IN); //读入DS18B20拉低信号
while(s3c2410_gpio_getpin(DQ)); //等待DS18B20应答
while(!s3c2410_gpio_getpin(DQ)); //等待DS18B20释放总线
}
void write_ds18b20(unsigned char Data) //写命令到ds18b20
{
unsigned char i;
s3c2410_gpio_cfgpin(DQ, DQ_OUT); //设置为输出
s3c2410_gpio_pullup(DQ, 1); //上拉
for(i=0;i<8;i++){
s3c2410_gpio_setpin(DQ, 0); //拉低总线
udelay(10); //需要拉低10~15us
if(Data&0x01)
s3c2410_gpio_setpin(DQ, 1);
else
s3c2410_gpio_setpin(DQ, 0);
udelay(40); //需要拉低20~40us来写0
s3c2410_gpio_setpin(DQ, 1); //释放总线
udelay(1); //稍微延时
Data >
>= 1;
}
}
static unsigned char read_ds18b20(void) //读ds18b20
{
unsigned char Temp=0,i;
for(i=0;i<8;i++){
Temp >>= 1;
s3c2410_gpio_cfgpin(DQ, DQ_OUT); //DQ为输出状态
s3c2410_gpio_setpin(DQ, 0); //拉低总线，启动输入
udelay(1); //拉低总线约1us
s3c2410_gpio_setpin(DQ, 1); //释放总线
s3c2410_gpio_cfgpin(DQ, DQ_IN); //DQ为输入状态
if(s3c2410_gpio_getpin(DQ))
Temp |= 0x80;
udelay(45); //延时45us
}
return Temp;
}
static int ds18b20_open(struct inode *inode,struct file *filp)
{
filp->private_data = ds18b20_devp;
ds18b20_reset();
printk(KERN_NOTICE "open ds18b20 successful\n");
return 0;
}
static ssize_t ds18b20_read(struct file *filp,char __user *buf,size_t size,loff_t *ppos)
{
unsigned long err;
struct ds18b20_dev *dev = filp->private_data;
unsigned char result[2] = {0x00, 0x00}; //这个是用来存放从ds18b20读到的值
ds18b20_reset(); //reset ds18b20
write_ds18b20(0xCC); //跳过ROM
write_ds18b20(0x44); //温度转换
ds18b20_reset(); //reset ds18b20
write_ds18b20(0xCC); //跳过ROM
write_ds18b20(0xbe); //读取RAM
result[0] = read_ds18b20(); //读低8位，存放在result[0]
result[1] = read_ds18b20(); //读高8位，存放在result[1]
ds18b20_reset();
err = copy_to_user(buf, &result, sizeof(result));
return err -EFAULT : min(sizeof(result), size);
}
static int ds18b20_release(struct inode *inode,struct file *fil